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Logically it could be true to say: "All human beings are mortal (and therefore Peter is mortal because Peter is a human being)."

But the above statement could be false in a sense, because mortality is not the one and only property of a human being. A real-world argumentation could be similar:

"The purpose of this regulation is to improve the privacy of people."

But the purpose of the regulation is not only to improve the privacy of people (it could also be to improve their safety) and therefore the statement is not entirely true.

Or similarly: "The flag of the United States of America is blue." The flag is blue, but that is not the one and only property of the flag.

Is there a name for this kind of "truth" where the criteria is that the statement must capture everything about the object in order to be perceived as true? How could one debate on these premises of argumentation, which are a bit a divergence from common logic?

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    This seems like a question about linguistic conventions, rather than logic, and so more suitable for English SE. No statement can capture "everything" about any real object, so there can be no such criteria of truth. But 'the' typically means 'the only', 'is blue' means 'is blue all over', etc., and using them differently without explanation is misleading. However, colloquial conventions are not part of "common logic". If there is doubt one should simply clarify what is meant to disambiguate before even starting to debate. If it is done intentionally to obfuscate that's another matter. – Conifold Dec 5 '19 at 20:51
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    "the above statement could be false in a sense, because mortality is not the one and only property of a human being." The statement "All men are mortals" is not a definition; it is a statement predicating the property of "mortality" of human being. It does not assert that mortality is the only property of humans. Thus, there is no sense according to which "it si false"; i can be falsified only finding an immortal man. – Mauro ALLEGRANZA Dec 6 '19 at 11:41
  • The short answer is no, because determining EVERYTHING about an object is not possible a priori. To find answers to the question of what is true, you need to study epistemology and theories of truth. Correspondence, coherence, pragmatism, semantic, deflation, and disquotationalism are venerable distinctions. en.wikipedia.org/wiki/Truth – J D Dec 6 '19 at 16:09
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A distinction between a statement which describes the essential properties of an object and one which describes only contingent properties is the key point.

For instance, 'A triangle is a a plane figure with three straight sides and three angles', states all the definitional properties of a triangle - hence in this specific sense it captures everything (definitionally) true of the object - but leaves out (indefinitely many) contingent features such as as the area of the triangle which are definitionally irrelevant. In this second sense it plainly does not 'capture everything about the object'. No statement could capture strictly everything, could include every property - monadic properties, polyadic properties, properties of properties of properties, properties of properties of properties and so on and on.

Essentialism and essential properties involve us in all manner of difficulties and worse in regard to natural kinds. But regulations and flags are not natural kinds; and I offer the answer above as clariificatory of at least a part of your problem. Hope it helps.

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It depends on what the meaning of "is" is.

But seriously, the problem here is not so much one of logic but rather of clarity of intended meaning.

"The" and "is" in your presented uses are at best ambiguous (at worst purposefully misleading and false). "The purpose" can be interpreted as "The [only/main] purpose" or better expressed as "A purpose". "is blue" tends to understood as "is [mostly/all] blue", where "has blue" is a more precise statement.

Once the wording of the statements are clarified, these problems disappear.


The original statement could not be false if all the premises are true. The first premise is claiming a property of all humans, other/all properties are not relevant.

Any failure of the original argument would be due to false premises.

For example: "All human beings have two legs (and therefore Peter must have two legs because Peter is a human being)." Fails if Peter is an amputee or was born different. It is not the logic that is flawed, but the premise does not capture the truth precisely.

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The data you provide are a mixed bag. so it's not quite clear what you are aiming at. The purpose-sentence is pragmatically quite odd, since the definite noun phrase pragmatically conveys that there's only one purpose. Equally, the lack of restricting modifiers of the adjective 'blue' indicates that all proper parts of the flag are blue.

There may be contexts where these sentences convey acceptable meanings and probably it's these contexts you have in mind. But in any case these meanings could be rendered more effectively by adding modifiers so to yield the likes of 'the main purpose', 'partially blue'.

Adding these modifiers also allows standard reasoning with such sentences. For instance, we can take the adverb 'partially' to denote a function f from properties to properties such that, for any Property P, f(P) is the property, that some individual has iff at least one of its proper parts has P. Take 'the' to denote the relation THE between two properties P,Q such that THE(P, Q) holds iff P applies to exactly on object and all Ps are Qs. Finally assume that 'is' denotes the identity function and both 'flag' and 'blue' denote properties. Under this assumptions and letting [ ] be a function sending expressions to their denotations, the flag-sentence is true iff [the] applies to the pair ([flag], ([partially][blue])) iff there is exactly one flag with a blue proper part.

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This is just a common logical fallacy: fallacy of composition, assuming that the whole is X because a part is X.

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